Desenvolvimento de compósitos flexíveis de PVDF/BaTiO₃ para aplicações eletromecânicas

Abstract

The use of renewable energy sources contributes to reducing greenhouse gas emissions and mitigating the impacts of climate change. In this context, flexible composites based on poly(vinylidene fluoride)/barium titanate (PVDF/BaTiO3) have gained prominence in electromechanical applications, such as sensors and actuators, due to their combination of flexibility with favorable dielectric and piezoelectric properties. The efficiency of these composites depends directly on the structural, morphological, and dielectric characteristics of the BaTiO3 particles used as functional fillers. This work investigated the solid-state synthesis of BaTiO3 with sonochemical activation, evaluating different combinations of lowcost, lead-free, and environmentally friendly barium and titanium precursors. The combinations included BaCO3, Ba(NO3)2, C4H6BaO4, paired with C12H28O4Ti or TiO2, with pH used as an additional synthesis parameter. The results indicated that the combination of C4H6BaO4 and TiO2 favored the formation of the desired tetragonal phase. Sonochemical activation enhanced precursor reactivity, allowing a reduction in synthesis time and temperature to approximately 900°C. A pH variation between 2 and 12 significantly influenced the formation of the tetragonal phase, with pH 6 yielding optimal results, producing powders with 92.92% tetragonal phase, high purity, and a dielectric constant of approximately 1200. This material was used to fabricate flexible PVDF/BaTiO3 composites with different filler contents (2.5%, 5%, 7.5%, and 10% by weight). The composites showed increased β-phase content in PVDF, enhanced crystallinity, and dielectric properties. A 2.5 wt.% BaTiO3 amount increased tensile strength by 9%, while 10 wt.% raised the dielectric constant by approximately 36%. These findings highlight the importance of precise control over composition and synthesis parameters for developing scalable, lead-free composites with potential for electromechanical applications.